Pilot circuit switch



April 18, 1944. E. MucHow PILOT CIRCUIT SWITCH Filed Nov. 2l, 1941 laf/.sm 1.

EL ME@ Mac/40W,

Patented Apr. 18, 1944 PILOT CmCUlT SWITCH Elmer Mucliow, Maplewood, Mo., assignor to Au ton-natio Control Corporation, St. Louis, M0., a corporation of Missouri Application November 21, 1941, Serial No. 419,881

3 Claims.

The present invention relates to an electric switch, and more particularly to a combination including a pilot circuit switch that may be employed in connection with a main switch so as to relieve arcing at the main switch.

The invention comprises in general e. main switch of a particularly desirable construction, that may be subject to arcing, because oi vibration of the contacts due to impact when the oontacts are closed, and a pilot switch that is closed when this vibration oi' the main switch occurs, which pilot switch is not subject to arcing from the vibration, and which is sufficient to carry enough load in parallel with the main switch to avoid arcing of the main switch.

An object of the invention is to provide such a pilot switch as above described.

A broad object is to provide in combination with the main switch, subject to vibration and arcing, a pilot switch not subject to arcing because of vibration, which pilot switch is closed in suincient time with respect to the vibration of the main switch to carry adequate load to prevent the arcing at the main switch.

Specifically, an object is to provide contacts and contact support for the pilot switch, enabling the contacts to vibrate together without breaking upon closure and to combine this pilot switch with the main switch, and means operated by operation of the main switch to actuate the pilot switch at or upon the operation of the main switch.

A further object is to provide a novel series of linkages and levers for operating the two switches, including means to provide a difierential between the opening and closing values of the switches.

A further object is to provide a connector called a jumper, located so as to be readily ref movable to eliminate one of the two switches from the circuit or to re-insert said switch in the circuit as desired.

In the drawing:

Figure l is a front view of the switch;

Fig. 2 is a vertical medial section on the line 2-2 of Fig. 1;

Fig. 3 is va fragmental vertical section taken on the line 3-3 of the lower left hand part of Fig. 2;

Fig.- 4 is a fragmental vertical section taken at the lower middle part of Fig. 2;

Fig. 5 is a broken horizontal section taken 4on the line 5 5 at the lower part of Fig. 2;

Fig. 6 is a fragmental section similar to the lower part of Fig. 2, but with the switch in its other position; and,

Fig. 7 is a diagram of the connections in the switch mechanism.

The switch is mounted upon a front panel it. A channelshaped casing il has 'its iianges secured to the panel it and forms side walis i2 and i3 and a back wall iii ior the switch.

A primary lever, generally indicated at l5, is pivoted on the pivot l5 to a dierential lever Il', pivoted at lil 'to the side walls iii and lf3. The differential lever, in turn, has an opstandn ing portion le attached by a spring hinge to a correspondingly upstanding portion @i a secondary lever generaliy indicated 22.

l The primary lever has, as a powerureceiving end, a lower portion disposed opposite an @penn ing i3 in the loa-ci: wall it, and also opposite a notch 211 extending upward from the end ci the dierential lever il. A power stud 25 adapted to pass through the opening 23, the notch t and abut against the end oi the primary lever. ihis stud is adapted to be driven by a movable diaphragm, such as is well known in the art, oi; oy any suitable element, such as one moved in response to temperature or pressure changes. In the device shown, the member 25 moves to ward the panel it upon increase in temperature or pressure. The stud 25 has a head 26 engageable over the edges oi the notch 2li, to apply force onto the differential lever when the stud moves backwardly.

The primary lever, at its upper end has a notch providing lugs 2B that straddle a dineren-f` tial adjusting screw 2e, that is adjustably threaded at 3U into the differential lever I1. The screw 29 is provided with a fixed flange 3i to receive the lugs 28 on one side and to receive an extending end 32 of the spring hinge 20 on the other side, which is serrated. This spring normally exerts a force toward the front panel lil and thereby restricts fortuitous displacement of the screw. The screw extends through an opening 33 in the front panei ill and is kerfed at its outer end to receive a screw driver for adjustments.

The secondary lever 22 at its lower end is provided with a resilient yieldable portion 36 that is bent, toward its lower end, to have a horizontal portion 3l, and additionally bent to have an end portion 38, tov which are attached two armature members 39 and 40 iixed in spaced relationship by a connector 4l.

On the portion 3G of the secondary lever is supported a Contact bar 42 adapted to span two contacts 43 and 44, as will appear. The contact ibar 42 is generally T-shaped as appears in Fig. 4. Its upper end is bifurcated to engage about a T-shaped element 45 secured to the secondary lever 36 and adapted to permit limited displacement in a swivelling manner of the upper end o the contact bar 42. The lower end of the contact bar is provided with a tongue 41 engaging through a slot in the portion 31 of the secondary lever which slot permits limited movement of the end of the contact bar relative to the lever portion 31, toward and from the panel it.

Centrally of the contact bar 42 is a pin 49 passing through an opening in the portion 3@ of the secondary lever, and adapted to be engaged by the end of a leaf spring 5E! secured between this upper portion and the lower portion 36 of the secondary lever. These three members are riveted together as appears at 5i in Fig. 4.

The contact 43 is held to the inside of the panel ID by a bridge member 53, as shown in Fig. 5. A terminal 54 is secured to the panel and to the bridge 53 to bring a lead to the bridge.

Similarly the contact 44 is provided with a bridge 55 and a terminal 56.

'Ihe armature member of the secondary lever disposes the armature elements 33 and 40 on opposite sides of magnetic poles 58 and 53. These magnetic poles have extensions 60 and 6i to act as a, blow-out means, all as shownin Patent No. 2,250,016 issued to Claude M. Garner von July 22, 1941. A magnetic element 62 provides magnetic energy for the pole pieces, and all are secured together in a plastic block attached to the panel wall i4.

A stop member 64 limits movement of the lower end of the secondary lever toward the front panel l0. The stop is connected with a support by a terminal post, generally indicated at 65. This terminal post supports an upwardly extending leaf spring 66 of conducting material, normally urged by inherent resiliency to shift its upper end backwardly from, the panel I0.

It has toward its upper end a contact 61 adapted to engage with an opposite contact 68 held on a U-shaped contact member 69 (Fig. 3) formed of conducting and leaf spring material y and attached at its other end to the terminal 54.

An adjustable screw 1i is threaded to be held in the secondary lever 2l and has an end adapt- -ed to engage the upper extension o f the member 66.

The terminal 65 has a screw 12 outside the front panel I0 which is adapted removably to hold a jumper 13 of conducting material across the terminals 65 and 5B.

This switch is adapted to be used for either alternating current or direct current and is ilexible so as to be capable of application to varying load conditions.

Operation ot the primary lever provides a direct lifting force upon the pivot I6 to displace the primary lever and the dierential lever about the pivot i8 of the latter, toward the front panel i0. The displacement of the diierential lever l1 with the primary lever displaces the hinge member i9 toward the front panel, which urges the upper end of the secondary lever 2i toward the front panel. This causes the secondary lever to pivot counterclockwise (Fig. 2) to urge the lower end of the secondary lever backwardly to bring the contact member 42 across the contacts 43 and 44. During the early part of the movement of the upper end of the secondary lever, the lower end, being retained by force of the magnetic eld on the armature 40, resists displacement. This action distorts the yieldable part of the secondary lever, accumulating energy until the stored force exceeds the resistance of the magnet. Then the lower end 'draws away from the magnet. As the force of the magnet varies with an exponent of the distance from the magnet, that force diminishes rapidly once the displacement of the lower end begins, effecting a snap action. When the other armature 39 enters the eld ofthe magnet, it reverses theaction, and closes with a snap action.

Despite the ilexibility of the `construction of the main switch, there is a bouncing action of the contact member 42 against the contacts 43 and 44 with accompanying arcing. Where the switch is carrying, for instance, an inductive load, this arcing can occur in serious proportion. To avoid this, the pilot switch including the contacts 61 and 68 is provided. The screw 1l is adjustable so that the upper end of the spring 66 is released to close the contacts 61 and 68 prior to closure of the switch member 42 against the contacts 43 and 44. Owing to the resiliency in construction of both the members 6B and 69, the contacts 61 and 68 vibrate together and, therefore, do not bounce Vto cause arcing. This pilot switch, therefore, carries the screw 25 moves backwardly, the end' of the pri- I6 is prevented, and further pressure on the end 75 mary lever l5 is permitted also to move backwardly. After traveling the amount permitted by the diierential adjustments, the head 26 of the screw 25 engages the forward surface of the diierential lever 24 and pulls it backwardly, causing the differential lever to pivot about the pivot i8 in a clockwise direction, and to draw with it the seccndary lever 2l so that the latter pivots clockwise to open the switch. In this action, the contacts 42, 43 and 44 are broken before the contact 61 and are parted. But the action of the pilot switch in both opening and closing is controlled by the snap-action mechanism.

The foregoing switch may be used with the connection described, and the jumper 13 in, for an A. C. inductive load, such as for a motor load of 1% H. P. A. C. In such case, the pilotswitch prevents arcing because of vibration of the main contacts. With the jumper out and the main switch only in circuit, the switch may be used for a non-inductive load A. C. or D. C. or for a direct current load. With the jumper out and connections made from the terminal l to the terminal 65, the pilot switch may be used for relatively small A. C. loads.

What is claimed is:

l. In a switch mechanism, a casing, a switch lever movable in said casing, contact means on said switch lever, second contact means on the casing engageable by the contact means on the lever, a third contact, means resiliently supporting said third contact on the casing, a fourth contact engageable by said third contact, means resiliently supporting the fourth contact on the casing, said third and fourth contacts supporting means having similar vibration characteristics to cause said third and fourth contacts to vibrate together when brought into contact with each other, said first and second contacts being in parallel with said third and fourth contacts, means on the switch lever engaging one of said resilient contact mounting means when said switch lever is in position to open said main switch, said engaging means being adapted to release said contact supporting means in time to permit closing of said third and fourth contacts vby the time said iirst and second contacts are 2'. In a switch mechanism, a main switch including a, relatively rigid movable switch member and a relatively rigid contact engageable thereby, means moving the member toward said contact in such wise as to cause bouncing, a pilot switch including a second switch member and a contact member adapted to be engaged thereby, said pilot switch members having similar vibration characteristics and thereby being constructed to be free of bouncing and connected in parallel with the main switch, and means to close the pilot switch at the time the main switch is closing and subject to bouncing.

3. In a mechanism of the kind described, a base, a main switch including a rst contact relatively rigidly mounted on the base, a switch lever, and afsecond contact on the lever, automatic means including snap-action means to operate the lever to bring the second contact to the rst, said switch lever being relatively rigid whereby bouncing may occur when the contacts engage, an auxiliary switch including third and fourth contacts, means mounting the third and fourth contacts separately on the base, means operated upon movement of the lever to close the main switch to effect closure of the third and fourth contacts, said mounting means for said third and fourth contacts including a' relatively iiexible member yieldable when the fourth contact is brought against the third, to avoid bouncing, said auxiliary switch being in parallel with the main switch and said means for effecting closure of the auxiliary contacts being adapted to close the auxiliary switch by the time the main switch contacts meet, whereby the auxiliary switch may carry the current of the main switch when the contacts of the latter are bouncing.

ELMER MUCHOW. 

